Lake Tahoe is a major tourist attraction in both Nevada and California. It is home to a number of ski resorts, summer outdoor recreation, and tourist attractions. Snow and skiing are a significant part of the area's economy and reputation.[7][8] Mountain and lake scenery are attractions throughout the year. The Nevada side also includes large casinos. Highways provide year-round access from Reno, Carson City, and Sacramento.

Lake Tahoe is the second deepest lake in the U.S., with a maximum depth of 1,645 feet (501 m),[1][9] trailing only Oregon's Crater Lake at 1,949 ft (594 m).[9] Tahoe is also the 16th[10]deepest lake in the world, and the fifth deepest in average depth. It is about 22 mi (35 km) long and 12 mi (19 km) wide and has 72 mi (116 km) of shoreline and a surface area of 191 square miles (490 km2). Approximately two-thirds of the shoreline is in California.[11] The south shore is dominated by the lake's largest city, South Lake Tahoe, California, which adjoins the town of Stateline, Nevada, while Tahoe City, California, is located on the lake's northwest shore. Although highways run within sight of the lake shore for much of Tahoe's perimeter, many important parts of the shoreline lie within state parks or are protected by the United States Forest Service. The Lake Tahoe Watershed (USGSHuc 18100200) of 505 sq mi (1,310 km2) includes the land area that drains to the lake and the Lake Tahoe drainage divide traverses the same general area as the Tahoe Rim Trail.

Lake Tahoe is fed by 63 tributaries, which drain an area about the same size as the lake; half the water entering the lake is rain or snow falling directly on it.

The Truckee River is the lake's only outlet.[5] The Truckee flows northeast through Reno, Nevada, and into Pyramid Lake, Nevada, which has no outlet. Only one third of the water that leaves the lake leaves via the Truckee, however; the rest evaporates from the lake's vast surface.

The flow of the Truckee River and the height of the lake are controlled by a dam at the outlet.

The Lake Tahoe Basin was formed by vertical motion (normal) faulting. Uplifted blocks created the Carson Range on the east and the Sierra Nevada on the west. Down-dropped blocks (grabens) created the Lake Tahoe Basin in between.[1] This kind of faulting is characteristic of the geology of the adjoining Great Basin to the east.

Three principal faults form the Lake Tahoe basin: the West Tahoe Fault, aligned between Emerald Bay and Tahoe City, and which is the local segment of the Sierra Nevada Fault, extending on shore north and south of these localities;[14] the East Tahoe Fault, aligned along the eastern shoreline; and the North Tahoe Fault, which runs between the two others deep under the northern part of the lake.[15] The West Tahoe Fault appears to be the most active and potentially hazardous fault in the basin. A study in Fallen Leaf Lake, just south of Lake Tahoe, used seafloor mapping techniques to image evidence for paleoearthquakes on the West Tahoe and revealed the last earthquake occurred between 4,100 and 4,500 years ago.[16]

Some of the highest peaks of the Lake Tahoe Basin that formed during the process of Lake Tahoe creation are Freel Peak at 10,891 feet (3,320 m), Monument Peak at 10,067 feet (3,068 m), Pyramid Peak at 9,984 feet (3,043 m) (in the Desolation Wilderness), and Mount Tallac at 9,735 feet (2,967 m).[1] The north shore boasts three peaks at 10,000+ feet: Mount Rose, Houghton and Relay peaks. Mt. Rose is a very popular hiking and backcountry skiing destination.

Eruptions from the extinct volcanoMount Pluto formed a dam on the north side. Melting snow filled the southern and lowest part of the basin to form the ancestral Lake Tahoe. Rain and runoff added additional water.[17]

Modern Lake Tahoe was shaped and landscaped by scouring glaciers during the Ice Ages, which began a million or more years ago.

Soils of the basin come primarily from andesitic volcanic rocks and granodiorite, with minor areas of metamorphic rock. Some of the valley bottoms and lower hill slopes are mantled with glacial moraines, or glacial outwash material derived from the parent rock. Sandy soils, rock outcrops and rubble and stony colluvium account for over 70% of the land area in the basin. The basin soils (in the < 2 mm fraction) are generally 65-85% sand (0.05–2.0 mm).

Given the great depth of Lake Tahoe, and the locations of the normal faults within the deepest portions of the lake, modeling suggests that earthquakes on these faults can trigger tsunamis. Wave heights of these tsunamis are predicted to be on the order of 10 to 33 ft (3 to 10 m) in height, capable of traversing the lake in just a few minutes.[18] A massive collapse of the western edge of the basin that formed McKinney Bay around 50,000 years ago is thought to have generated a tsunami/seiche wave with a height approaching 330 ft (100 m).[19]

Mean annual precipitation ranges from over 55 inches (1440 mm) for watersheds on the west side of the basin to about 26 inches (660 mm) near the lake on the east side of the basin. Most of the precipitation falls as snow between November and April, although rainstorms combined with rapid snowmelt account for the largest floods. There is a pronounced annual runoff of snowmelt in late spring and early summer, the timing of which varies from year to year. In some years, summertime monsoon storms from the Great Basin bring intense rainfall, especially to high elevations on the northeast side of the basin.

August is normally the warmest month at the Lake Tahoe Airport (elevation 6,254 ft (1,906 m)) with an average maximum of 78.7 °F (25.9 °C) and an average minimum of 39.8 °F (4.3 °C). January is the coolest month with an average maximum of 41.0 °F (5.0 °C) and an average minimum of 15.1 °F (−9.4 °C). The all-time maximum of 99 °F (37.2 °C) was recorded on July 22, 1988. The all-time minimum of −29 °F (−33.9 °C) was recorded on December 9, 1972, and February 7, 1989. Temperatures exceed 90 °F (32.2 °C) on an average of 2.0 days annually. Minimum temperatures of 32 °F (0 °C) or lower occur on an average of 231.8 days annually, and minimum temperatures of 0 °F (−17.8 °C) or lower occur on an average of 7.6 days annually. Freezing temperatures have occurred in every month of the year.[20][21]

Vegetation in the basin is dominated by a mixed conifer forest of Jeffrey pine (Pinus jeffreyi), lodgepole pine (P. contorta), white fir (Abies concolor), and red fir (A. magnifica).[25] The basin also contains significant areas of wet meadows and riparian areas, dry meadows, brush fields (with Arctostaphylos and Ceanothus) and rock outcrop areas, especially at higher elevations. Ceanothus is capable of fixing nitrogen, but mountain alder (Alnus tenuifolia), which grows along many of the basin’s streams, springs and seeps, fixes far greater quantities, and contributes measurably to nitrate-N concentrations in some small streams. The beaches of Lake Tahoe are the only known habitat for the rare Lake Tahoe yellowcress (Rorippa subumbellata), a plant which grows in the wet sand between low- and high-water marks.[26]

Each autumn, from late September through mid-October, mature kokanee salmon (Oncorhyncus nerka), transform from silver-blue color to a fiery vermilion, and run up Taylor Creek, near South Lake Tahoe. As spawning season approaches the fish acquire a humpback and protuberant jaw. After spawning they die and their carcasses provide a feast for gatherings of mink (Neovison vison), bears (Ursus americanus), and Bald eagles (Haliaeetus leucocephalus). The salmon are not native and were transplanted from the North Pacific to Lake Tahoe in 1944.[27]

North American Beaver (Castor canadensis) were re-introduced to the Tahoe Basin by the California Department of Fish and Wildlife and the U.S. Forest Service between 1934 and 1949. Descended from no more than nine individuals, 1987 beaver populations on the upper and lower Truckee River had reached a density of 0.72 colonies (3.5 beavers) per kilometer.[28] At the present time beaver have been seen in Tahoe Keys, Taylor Creek, Meeks Creek at Meeks Bay on the western shore, and King's Beach on the north shore, so the descendants of the original nine beavers have apparently migrated around most of Lake Tahoe.[29][30] Recently novel physical evidence has demonstrated that beaver were native to the Sierra until at least the mid-nineteenth century, via radiocarbon dating of buried beaver dam wood uncovered by deep channel incision in the Feather River watershed.[31] That report was supported by a summary of indirect evidence of beaver including reliable observer accounts of beaver in multiple watersheds from the northern to the southern Sierra Nevada, including its eastern slope.[32] A recent study of Taylor Creek showed that beaver dam removal decreased wetland habitat, increased stream flow, and increased total phosphorus pollutants entering Lake Tahoe - all factors which negatively impact the clarity of the lake's water.[33] In addition, beaver dams located in Ward Creek, located on the west shore of Lake Tahoe, were also shown to decrease nutrients and sediments traveling downstream.[33]

The lake's cold temperatures and extreme depth can slow the decomposition rate of organic matter. For example, a lost diver was found 17 years later at a depth of 300 feet (90 m), with his body preserved nearly perfectly.[34]

The area around Lake Tahoe was originally inhabited by the Washoe tribe of Native Americans. Lake Tahoe was the center and heart of Washoe Indian territory, including the upper valleys of the Walker, Carson and Truckee Rivers. The English name for Lake Tahoe derives from the Washo word “dá’aw," meaning “Lake”.[4]

Lt. John C. Frémont was the first person of European descent to see Lake Tahoe, during Fremont's second exploratory expedition on February 14, 1844.[35]John Calhoun Johnson, Sierra explorer and founder of "Johnson's Cutoff" (now U.S. Route 50), was likely the first white man to see Meeks Bay and from a peak above the lake he named Fallen Leaf Lake after his Indian guide. His first job in the west was in the government service, carrying the mail on snowshoes from Placerville to Nevada City, during which time he named the lake "Lake Bigler" in honor of California’s third governor John Bigler.

In 1853 William Eddy, the surveyor general of California, identified the lake as Lake Bigler. During the Civil War, Union advocates objected to the name, because Bigler was an ardent secessionist. Due to this, the U.S. Department of the Interior introduced the name Tahoe in 1862. Both names were in use: the legislature passed legislation declaring the official name to be Lake Bigler in 1870, while to most surveys and the general public it was known as Lake Tahoe.[36] The lake didn't receive its official and final designation as Lake Tahoe until 1945.

Upon discovery of gold in the South Fork of the American River in 1848, thousands of gold seekers going west passed near the basin on their way to the gold fields. European civilization first made its mark in the Lake Tahoe basin with the 1858 discovery of the Comstock Lode, a silver deposit just 15 miles (24 km) to the east in Virginia City, Nevada. From 1858 until about 1890, logging in the basin supplied large timbers to shore up the underground workings of the Comstock mines. The logging was so extensive that loggers cut down almost all of the native forest.[37]

The only outlet of Lake Tahoe and the headwaters of the Truckee River at Lake Tahoe Dam

While Lake Tahoe is a natural lake, it is also used for water storage by the Truckee-Carson Irrigation District (TCID). The lake level is controlled by a dam built in 1913 at the lake's only outlet, the Truckee River, at Tahoe City. The 18-foot (5.5 m) high dam can increase the lake's capacity by 744,600 acre·ft (918,500 dam3).[38]

During the first half of the 20th century, development around the lake consisted of a few vacation homes. The post-World War II population and building boom, followed by construction of gambling casinos in the Nevada part of the basin during the mid-1950s, and completion of the interstate highway links for the 1960 Winter Olympics held at Squaw Valley, resulted in a dramatic increase in development within the basin. From 1960 to 1980, the permanent residential population increased from about 10,000 to greater than 50,000, and the summer population grew from about 10,000 to about 90,000.[37] Since the 1980s, development has slowed due to controls on land use.

After a dispute that included gunshots exchanged between militia, in 1864, California and Nevada defined a partition that followed geographical coordinates: the state line runs east of the approximate center line of the lake; at 39 degrees north latitude, the state border runs southeasterly towards the Colorado River. Unbeknownst to the negotiators, this compromise split Lake Tahoe: two-thirds for California, one-third for Nevada.[39][40]

In California, Lake Tahoe is divided between Placer County and El Dorado County. In Nevada, Lake Tahoe is divided among Washoe County, Douglas County and Carson City (an independent city). The Tahoe Regional Planning Agency (TRPA) is a bi-state compact between California and Nevada, that is charged with environmental protection of the Lake Tahoe Basin through land-use regulation and planning.[41] Schisms between TRPA and local residents led to the formation of grass-roots organizations that hold firm to strict environmentalism.[42]

Lake Tahoe is also the location of several 19th and 20th century palatial homes of historical significance. The Thunderbird Lodge built by George Whittel Jr once included nearly 27 miles (43 km) of the Nevada shoreline. Vikingsholm was the original settlement on Emerald Bay and included an island teahouse and a 38 room home. The Ehrman Mansion is a summer home built by a former Wells Fargo president in Sugar Pine Point and is now a state park.

An example of road runoff with fine sediment at El Dorado Beach. However, this storm drain was removed during construction. The new beach now called Lakeview Commons opened in Summer 2012.

Despite land-use planning and export of treated sewage effluent from the basin, the lake is becoming increasingly eutrophic (having an excessive richness of nutrients), with primary productivity increasing by more than 5% annually, and clarity decreasing at an average rate of 0.25 meters per year.[43] Until the early 1980s, nutrient-limitation studies showed that primary productivity in the lake was nitrogen-limited. Now, after a half-century of accelerated nitrogen input (much of it from direct atmospheric deposition), the lake is phosphorus-limited. Swift[44] concluded that “suspended inorganic sediments and phytoplanktonic algae both contribute significantly to the reduction in clarity, and that suspended particulate matter, rather than dissolved organic matter, are the dominant causes of clarity loss.” The largest source of fine sediment particles to Lake Tahoe is urban stormwater runoff, comprising 72 percent of the total fine sediment particle load.[45] The urban uplands also provide the largest opportunity to reduce fine sediment particle and phosphorus contributions to the lake. Historic clarity of approximately 30 meters can be achieved with total reduction of approximately 75% from urban sources.[46]

Historically, the clarity of Lake Tahoe has been decreasing, with the rate of decrease slowing.[47] However, the lake's clarity has increased from 2011 to 2013, improving by over 10 percent.[48] Fine sediment, much of it resulting from land disturbance in the basin, accounts for about half of the loss in clarity. The year 2010 had a low average Secchi depth, with the depth of 64.4 feet being the second lowest ever recorded (the lowest was 64.1 feet in 1997). It represents a decrease of 3.7 feet from the previous year.[47]

Lake Tahoe never freezes.[50] Since 1970, it has mixed to a depth of at least 1,300 ft (400 m) a total of 6 or 7 times. Dissolved oxygen is relatively high from top to bottom. Analysis of the temperature records in Lake Tahoe has shown that the lake warmed (between 1969 and 2002) at an average rate of 0.015 °C per year. The warming is caused primarily by increasing air temperatures, and secondarily by increasing downward long-wave radiation. The warming trend is reducing the frequency of deep mixing in the lake, and may have important effects on water clarity and nutrient cycling.

Since the 1960s, the Lake's food web and zooplankton populations have undergone major changes. In 1963–65, opossum shrimp (Mysis diluviana) were introduced to enhance the food supply for the introduced Kokanee salmon (Oncorhynchus nerka). The shrimp began feeding on the lake's cladocerans (Daphnia and Bosmina), and their populations virtually disappeared by 1971.[51] The shrimp provide a food resource for salmon and trout, but also compete with juvenile fish for zooplankton. Since the 1970s, the cladoceran populations have somewhat recovered, but not to former levels.

In June 2007, the Angora Fire burned approximately 3,100 acres (1,300 ha) throughout the South Lake Tahoe area. While the impact of ash on the lake's ecosystem is predicted to be minimal, the impact of potential future erosion is not yet known.[52]

Until recently, construction on the banks of the Lake had been largely under the control of real estate developers. Construction activities have resulted in a clouding of the lake's blue waters. Currently, the Tahoe Regional Planning Agency is regulating construction along the shoreline.[53] (and has won two Federal Supreme Court battles over recent decisions). These regulations are unpopular with many residents, especially those in the Tahoe Lakefront Homeowners Association.[54]

The League to Save Lake Tahoe (Keep Tahoe Blue) has been an environmental watchdog in the Lake Tahoe Basin for 50 years.[55] Founded when a proposal to build a four-lane highway around the lake—with a bridge over the entrance to Emerald Bay—was proposed in 1957, the League has thwarted poorly designed development projects and environmentally unsound planning. The League embraces responsible and diversified use of the Lake's resources while protecting and restoring its natural attributes.[56]

Since 1980, the Lake Tahoe Interagency Monitoring Program (LTIMP) has been measuring stream discharge and concentrations of nutrients and sediment in up to 10 tributary streams in the Lake Tahoe Basin, California-Nevada. The objectives of the LTIMP are to acquire and disseminate the water quality information necessary to support science-based environmental planning and decision making in the basin. The LTIMP is a cooperative program with support from 12 federal and state agencies with interests in the Tahoe Basin. This data set, together with more recently acquired data on urban runoff water quality, is being used by the Lahontan Regional Water Quality Control Board to develop a program (mandated by the Clean Water Act) to limit the flux of nutrients and fine sediment to the Lake.

UC Davis remains a primary steward of the lake. The UC Davis Tahoe Environmental Research Center is dedicated to research, education and public outreach, and to providing objective scientific information for restoration and sustainable use of the Lake Tahoe Basin.[57] Each year, it produces a well-publicized “State of the Lake” assessment report.

During ski season, thousands of people from all over Nevada and California, including Reno, Las Vegas, Los Angeles, San Diego, San Francisco, and Sacramento, flock to the slopes for downhill skiing. Lake Tahoe, in addition to its panoramic beauty, is well known for its blizzards.[7]

The majority of the ski resorts in the Lake Tahoe region are on the northern end of the lake, near Truckee, California and Reno, Nevada. Kirkwood, Sierra-at-Tahoe and Heavenly are located on the southern side of the lake, 55–75 miles (90–120 km) from Reno. Scattered throughout Tahoe are public and private sled parks. Some, such as Granlibakken are equipped with rope tows to help sledders get up the hill.

During late Spring to early Fall, the lake is popular for water sports and beach activities. The two cities most identified with the Lake Tahoe tourist area are South Lake Tahoe, California and the smaller Stateline; smaller centers on the northern shoreline include Tahoe City and Kings Beach.

Other popular activities include parasailing, jet ski rentals and eco-friendly paddle sport rentals. There are rental locations located around Lake Tahoe. Kayaking and stand up paddle boards have also become very popular.

Boating is a primary activity in Tahoe in the summer. The lake is home to one of the most prestigious wooden boat shows in the country, the Lake Tahoe Concours d'Elegance, held every August. There are lake front restaurants all over the lake, most equipped with docks and buoys (See the restaurants section). There are all sorts of boating events, such as sailboat racing, firework shows over the lake, guided cruises, and more. As an interstatewaterway, Lake Tahoe is subject to the United States Coast Guard. Lake Tahoe is home to Coast Guard Station Lake Tahoe.[58]

SCUBA diving is popular at Lake Tahoe, with some dive sites offering dramatic drop-offs or wall dives. Diving at Lake Tahoe is considered advanced due to the increased risk of decompression sickness (DCS) while diving at such a high altitude.[59][60]

Fred Rogers became the first person to swim the length of Lake Tahoe in 1955, and Erline Christopherson became the first woman to do so in 1962.[61][62]

There are numerous hiking and mountain biking trails around the lake. They range widely in length, difficulty and popularity. One of the most famous of Tahoe's trails is the Tahoe Rim Trail, a 165-mile (270-km) trail that circumnavigates the lake. Directly to the west of the lake is the Granite Chief Wilderness, which provides great hiking and wilderness camping. Also, to the southwest is the very popular Desolation Wilderness. One of the most popular trailheads used to access these popular destinations is Eagle Lake Trailhead, located near Emerald Bay on Tahoe's west shore. The Flume Trail of the east shore is one of Mountain Biking Magazine's Top 10 Trails in the U.S. There are also many paved off-road bicycle paths that meander through communities on all sides of the lake.

Gambling is legal on the Nevada side of Lake Tahoe. Casinos, each with a variety of slot machines and table games, are located on the South Shore in Stateline, and on the North Shore in Crystal Bay and Incline Village.

When Nevada legalized gambling in 1931, the first casino at the lake had already been open for years. First built on the North Shore in Crystal Bay by Robert Sherman in 1926,[63] the Calneva cabin became the property of Norman Henry Biltz and was sold to Bill Graham and Jim McKay in 1929.

The Calneva was rebuilt after a fire in 1937 and expanded several times, most noticeably in 1969 when the high-rise hotel was built. Along the way, Frank Sinatra owned the property in the early 1960s, shared his cabins with the likes of Sam Giancana and Marilyn Monroe, and sold out at the height of the area's popularity.

Other casinos at the North Shore include the Crystal Bay Club, first built in 1937 as the Ta-Neva-Ho; the Tahoe Biltmore, and the Nugget. The Hyatt Regency is found at Incline Village.

At South Shore, Bill Harrah purchased the Stateline Country Club which had stood since 1931 and built Harrah's Tahoe. Other casinos include Hard Rock Hotel & Casino Lake Tahoe, Harvey's, Montbleu, and the Lakeside Inn.

Visitors can reach Lake Tahoe under ideal conditions within two hours from the Sacramento area, one hour from Reno or thirty minutes from Carson City. In winter months, chains or snow tires are often necessary to reach Tahoe from any direction. Traffic can be heavy on weekends due to tourists if not also from weather.

The primary routes to Lake Tahoe are on Interstate 80 via Truckee, U.S. Route 50, and Nevada State Route 431 via Reno. Most of the highways accessing and encircling Lake Tahoe are paved two-lane mountain roads. US 50 is a four-lane highway (from the canyon of the South Fork American River at Riverton, over the Sierra Nevada at Echo Summit, and into the Lake Tahoe Basin, is a mainly two-lane road) passing south of the lake and along part of the eastern shore.

California State Route 89 follows the western shore of the lake through the picturesque wilderness and connects camping, fishing and hiking locations such as those at Emerald Bay State Park, DL Bliss State Park and Camp Richardson. Farther along are communities such as Meeks Bay and Tahoe City. Finally, the highway turns away from the lake and heads northwest toward Truckee.

California State Route 28 completes the circuit from Tahoe City around the northern shore to communities such as Kings Beach, Crystal Bay, and into Incline Village, Nevada where the road becomes Nevada State Route 28. Route 28 returns along the eastern shore to US 50 near Spooner Lake.

The Ponderosa Ranch of the TV series Bonanza was formerly located on the Nevada side of Lake Tahoe.[64] The opening sequence of the TV series was filmed at the McFaul Creek Meadow, with Mount Tallac in the background. In September 2004 the Ponderosa Ranch closed its doors, after being sold to developer David Duffield for an undisclosed price.[65][66]

The 1974 film The Godfather Part II used the lakeside estate Fleur de Lac as the location of several scenes, including the elaborate First Communion celebration, the Senator's shakedown attempt of Michael, the assassination attempt on Michael, Michael disowning Fredo, Carmela Corleone's funeral, Fredo's death while fishing, and the closing scene of Michael sitting alone outside. Fleur de Lac, on the western California shore of Lake Tahoe, was formerly the Henry Kaiser estate. The surrounding lakeside area has been developed into a private gated condominium community and some of the buildings of the "Corleone compound" still exist, including the boathouse.[67]